Stereo Advantage’s high-tech sound systems fitted into outlandishly flashy stereo cabinets turn dull commutes into parties. Far from simply retrofitting cars for iPods and Bluetooth technology, the interior renovators outfit autos with all manner of speakers. Their gadgets are as much statement pieces as they are technological upgrades. The designers pride themselves on finding ways to blend sound-systems seamlessly into the car’s aesthetic. To complement their audiovisual equipment, they also offer an array of alarms, navigation systems, and remote starters.